Process for the distillation of coal tar and device for carrying out such process



PROCESS FOR THE DISTILLATION OF COAL TAR AND 'il. 'y 14. 1931. [wEssEL 1,814 989 DEVICE FOR CARRYING OUT SUCH PROCESS Filed June 18, 1927 /n v en ton.- Car/ Weasel Patented July 14, 1931 Units-n STATES or-mics CARL WESSEL, 0F -ESSEN.-IBQRBECK,'GERMANY PROCESS Eon-THE DISTILLATION 0F GOAL TAB AND DEVICE FORKGARRYING our SUCH PROCESS Application filed June 18, 1927, Serial 'No."199',813, and. iii-Germany June29f1926.

Asa rule, stills made of wrought iron are generally used inthe processes hitherto familiar forithe distillation of coal tar. {In these stills, heatis applied to the tar indirect by means of flue gases, superheated steam, or other carriers of heat, which strike against the wall of the still or against -a special heater. The several constituents of the tar such as waterylight oil, middle oil with naphthalene, heavy oil with naphthalene and anthracene oil with .anthracene, which boil at atemperature up toabout 400Celsius, are brought one after-another into a form of vapour as each ,attains'itsparticular boiling point and is distilled off. The residue remaining in thesti ll consists of pitch which is run off in the heatedstate.

In large plants, before the-processsproper of distillation takes place, the water and. light w oil are extracted from the tar in special de- 21;. period of some five to eight days the naphthalene is precipitated in the form of firm crystals, the oil can then be drained off the pans leaving the naphthalene crystals behind. The naphthalene in this condition still encloses a great deal of oil and is dried in a centrifugal machine. After an intensive treatment in the centrifugal machine, the oil content of the naphthalene is reduced to about 20 per cent.

As contrasted with the known processes,

the various constituents of the tar, in accordance with the present invention, are not separated from each other and one after the other at their respective boiling points, but the naphthalene and, where present, the light oil {and the water contained in the-tar are separated by means ofisteam-passed' directly into the distilling vessel. By theme of direct actingsteam, the naphthalene, the boiling point of whichis in the neighbourhood of 230 Celsius and which in the method usually employed: hitherto is found between 210 and280-Celsius in the middle oil and heavy oil fraction, is distilled off from'the tar at a temperature ofslightly more than 100 Celsius.

Preferably .the itar'is heated .(from an extraneous source of heat;)' either before or during the introduction of the steamto a temperature equal to ,or higher thanthe temperature of the incoming steam, :in order to avoid as much as possible "any increase of the Watercontained inthetar. It is immaterial Whether or no zthe'water has been previously separated from the tar.

By means of suitable dephlegmation the distillation vapours containing steam can be collected and-separated in light oil and water and further in naphthalene and water in liquid form. The separation of the light oiland naphthalene from the water, owing to the difference in their specificvgravities, can be eifected .easily and clearly in the usual way.

The naphthaleneproduced in accordance with the-present invention-is anhydrous after ithas been allowed to cool and contains-moreover only traces of oil. For purposes of crystallization the necessary pans-are C0111- paratively small, because the naphthalene content amounts .to only about one-eighth to one-tenth ofthemiddle and heavy oils. The use of the centrifugal machine which is so burdensome'to the workmen and which takes up a great dealo-f time is dispensed with.

Themiddle oil and theheavy oil passing over after removal of the naphthalene is, in accordance with thenew process, completely free of naphthalene, so that so far as these oils are concerned the cooling process in the crystallization pans whic'htakes up such a great deal of time becomes superfluous. Hitherto it .hasonlybeenpossible to rid these oils of the naphthalene either by resorting to artificial cooling or by repeating the distillation.

The new process can also be applied with advantage to the production of so-called prer-fpared tar which is supposed to contain no erto had to be done.

In order to render a smooth and continuous distillation of hydrous tar possible, it is important that care should be taken to see that the steam is introduced smoothly and that there is an intimate intermixture of steam and tar, without the formation of any bubbles or froth.

A device suitable for carrying out the process is shown by way of example on the drawing in vertical section.

The still a is provided with a steam inlet pipe Z) which opens into an injection tube 0.

At its lower end the injection tube is provided with lateral openings'd, whilst the up per end is covered over by a hood 6. Below the hood 6 are the lateral outlet openings f. Somewhat below these outlet openings f in the injection tube 0 an overflow pipe 9 is arranged on the still a.

Underneath the still are arranged gas burners h by means of which the tar is heated. Above the still is arranged a column 2' and also a dephlegmator 7a. A pipe Z leads from the dephlegmator /e to a condenser m to which an inspection pot n is connected. Two pipes run from the latter to a receiver 0.

With the aid of the above devices the process is carried out as follows The still is filled with tar up to the overflow branch 9, the tar having been preferably previously heated to a temperature of about 100 Celsius. Vith the aid of the gas burners h the temperature in the still can be increased to any desired extent. Steam is now led in through the pipe 6. The steam rises in the injection tube 0 and is intimately mixed there with the tar. The formation of bubbles or froth is prevented by the hood 6. By means of the introduced steam, water, light oil and naphthalene are first of all evaporated out of the tar. The vapours arrive in the column 2' and in the dephlegmator where any middle oils that may have been mechanically carried away with the vapours are retained and led back again into the still. These middle oils having a high boiling point may also get into the dephlegmator in the form of vapour. The vapours issuing from the upper end of the dephlegmator are led through the pipe Z to the condenser m where they are condensed. The condensate flows through the inspection pot n into a receiver 0. The water in the receiver, is continuously separated from the other substances in the usual way. The naphthalene reaches the crystallization pans in a liquid state, whilst the light oil is led into the appropriate containers. As soon as no more naphthalene appears in the inspection pot n, the supply of steam is cut oif and the distillation of the tar is completed by increasing the temperature with the aid of the burners it until the distillation of middle oil, heavy oil, anthracene oil and anthracene on the other hand, the process can also be interrupted when it is aquestion of the production of prepared tar.

The process moreover can not only be carried out as a batch process, but can also be carried out continuously. In the latter case, fresh tar is continuously led to the upper end of the still a, (say through pipe g, or another pipe) whilst the prepared tar is being continuously drawn off at the lower end through a separate pipe not shown. In this case, of course, the further distillation of the tar in this still must be Waived.

I claim:

1. In a process of treating coal tar, the method which firstly comprises driving 01f water, light oils by heating up, then distilling off the naphthalene alone and separately by a current of steam passing directly into the tar at below the distilling temperature of the naphthalene oil, in which operation a restricted quantity of the tar is being subjected to the action of steam.

2. In a process of treating coal tar, the method which firstly comprises driving off water, light oils by heating up, then distilling ofi the naphthalene alone and separately by a current of steam passing directly into the tar at below the distilling temperature of the naphthalene oil, in which operation a restricted quantity of the tar is being subjected to the action of steam, and after the complete expulsion of naphthalene, heating again high enough to drive off the naphthalene oil, and condensing the said naphthalene and naphthalene oil separately from each other.

In testimony whereof I have atfixed my signature.

CARL WESSEL. 

